Modified valence force field approach for phonon dispersion: from zinc-blende bulk to nanowires

Paul, Abhijeet; Luisier, Mathieu; Klimeck, Gerhard

doi:10.1007/s10825-010-0332-9

Cited by 56 publications

(95 citation statements)

References 29 publications

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“…More information about the construction of Φ and the harmonic force constants can be found in Ref. 30,31 . The total Hamiltonian operator accounting for harmonic and anharmonic interactions can be written as…”

Section: Theory a Model Derivationmentioning

confidence: 99%

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Atomistic modeling of anharmonic phonon-phonon scattering in nanowires

Luisier

2012

Phys. Rev. B

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Phonon transport is simulated in ultra-scaled nanowires in the presence of anharmonic phononphonon scattering. A modified valence-force-field model containing four types of bond deformation is employed to describe the phonon bandstructure. The inclusion of five additional bond deformation potentials allows to account for anharmonic effects. Phonon-phonon interactions are introduced through inelastic scattering self-energies solved in the self-consistent Born approximation in the Nonequilibrium Green's Function formalism. After calibrating the model with experimental data, the thermal current, resistance, and conductivity of <100>-, <110>-, and <111>-oriented Si nanowires with different lengths and temperatures are investigated in the presence of anharmonic phononphonon scattering and compared to their ballistic limit. It is found that all the simulated thermal currents exhibit a peak at temperatures around 200 K if phonon scattering is turned-on while they monotonically increase when this effect is neglected. Finally, phonon transport through Si-Ge-Si nanowires is considered.

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Section: Theory a Model Derivationmentioning

confidence: 99%

“…The largest simulation domain considered in this work contains more than 20000 atoms that can oscillate along the x, y, and z directions. Surface atoms are also allowed to freely move 31 . Before starting with the thermal characteristics of the nanowires in Fig.…”

Section: B Homogeneous Si Nanowiresmentioning

confidence: 99%

Atomistic modeling of anharmonic phonon-phonon scattering in nanowires

Luisier

2012

Phys. Rev. B

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“…Under the harmonic approximation, the motion of atoms can be described by a dynamic matrix as [15]: (2) where dynamic matrix component between atoms 'i' and 'j' is given as shown in Ref. [14] by: After setting up the dynamic matrix, the following eigenvalue problem is solved to calculate the phononic dispersion:…”

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Calculation of Confined Phonon Spectrum in Narrow Silicon Nanowires Using the Valence Force Field Method

Karamitaheri

Neophytou

Taheri

et al. 2013

Journal of Elec Materi

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We study the effect of confinement on the phonon properties of ultra-narrow silicon nanowires of side sizes of 1 10nm . We use the modified valence force field method to compute the phononic dispersion, and extract the density of states, the transmission function, the sound velocity, the ballistic thermal conductance and boundary scatteringlimited diffusive thermal conductivity. We find that the phononic dispersion and the ballistic thermal conductance are functions of the geometrical features of the structures, i.e. the transport orientation and confinement dimension. The phonon group velocity and thermal conductance can vary by a factor of two depending on the geometrical features of the channel. The <110> nanowire has the highest group velocity and thermal conductance, whereas the <111> the lowest. The <111> channel is thus the most suitable orientation for thermoelectric devices based on Si nanowires since it also has a large power factor. Our findings could be useful in the thermal transport design of siliconbased devices for thermoelectric and thermal management applications.

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“…Contrasted with force fields for organic systems [13][14][15][16][17][18], this force field doesn't have terms like torsion angle rotations. VFF models of this form have been used to model the bulk diamond phonon spectrum [20], phonon spectra of bulk Si and Ge [21,22], as well as silicon nanowires by Paul et al [23]. These, however, are all single-element systems with no need to introduce atomic charges.…”

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confidence: 99%

“…As mentioned above, Paul et al [23] have used force fields to calculate the phonon spectra of Si nanowire. But Si is a system where atomic charge is not needed.…”

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confidence: 99%